This invention pertains to a novel method of packing capillary columns. More particularly, the invention pertains to a method of packing capillary columns by drawing a slurry of packing material into a capillary column through capillary action, and then removing solvent from the slurry through one end of the column.
There are a variety of methods currently in use for packing capillary columns, such as those columns used in the fields of chromatography and electrospray ionization mass spectrometry (ESI-MS). The most popular methods in current use are the so-called "slurry packing" methods.
U.S. Pat. No. 5,679,255 discloses a method whereby a retaining material, such as a ceramic frit which will allow solvent, but not packing material, to pass is placed in one end of the column. A slurry of polymeric packing material in an organic solvent, such as THF, is then pumped through the column, from the end opposite that having the retaining frit. The packing material thereby accumulates in the column, while the liquid portion of the slurry passes out through the frit. This method has certain disadvantages, however. The capillary tubing used must be capable of withstanding the pressure generated by the pumping of the slurry into the tube, and necessary equipment, such as a pump and solvent recovery system must be provided. High packing pressure may also cause deterioration of or damage to the packing material.
U.S. Pat. No. 4,483,773 discloses a method wherein an end restriction is first placed in a column, to permit the flow of solvent, but restrict the passage of particles out of the end of the column. A slurry is then caused to flow into the column, under pressure. A two-step pressure sequence is then used to first fill up the column and form a bed of particles and then to uniformly compress the bed. This method is less than completely satisfactory, because special equipment is required to practice it.
There is therefore a need for a simple, direct method for packing capillary columns, which does not rely on special equipment for pumping or pressurizing slurries into the columns.